Te masticatory reduction of food is a key preliminary to effective nutrient extraction, and the time and energy invested in chewing have been shown to vary with food type, consistency, and size as well as dentitional pattern. Food reduction involves more than simple linear or planar mandibular rotation (about the condyle); propalineal and transverse shifts are common, and mandibles move in a complex three-dimensional path. Food is reduced by being passed unidirectionally across the triturating surface when the teeth are nearest occlusion; during the rest of the mastication cycle, movements of tongue, lips, and the whole head return the bolus to the starting side of the active tooth row. The forces required to maintain the mandible in its path consequently vary. Control of the cycle involves matching muscular activity to the demands at different parts of the orbit, reflecting in part the position, size and consistency of the food. It is proposed to correlate movements and motor sequences in three mammals and three reptiles (possibly similar to precursors of early states of mammalian mastication), using wild (non-domesticated) animals, which have been conditioned to feed normally. Analysis will involve motion recording by cinematography, cinefluoroscopy, and strain gauge recording; the fiber types of the muscle will be characterized by histochemical assay, and fiber lengths and architecture determined, and their function during mastication noted by electromyography. From these data we hope to match muscle physiology and activity to the energy shifts of the moving system and to determine those aspects that seem to be maximized, and presumably most significant to the organism.